Optical fibers, carrying light signals, are currently one of the basic communication media. In order to allow flexibility in communications, efficient switches, which allow coupling different optical fibers to each other at different times, are required. Optical fiber switches are required to be durable, robust, easily repaired and require low maintenance costs.
U.S. Pat. No. 4,834,488 to Lee, titled: “Fiberoptic Switch”, the disclosure of which is incorporated herein by reference in its entirety, describes a switch in which a first fiber is rotated to be aligned with any of a plurality of fibers. This switch arrangement is not suitable for an M×N switch, in which any of M inputs can be connected to any of N outputs.
In M×N optical fiber switches it is generally required that any pair of input and output fibers can be connected or disconnected at any time, regardless of the connection state of the other fibers of the switch.
U.S. Pat. Nos. 4,955,686 to Buhrer et al., titled: “Optical Fiber Crossconnect Switch” and U.S. Pat. No. 5,050,955 to Sjolinder, titled: “Fiberoptic Switch”, the disclosures of both of which are incorporated herein by reference in their entirety, describe rectangular optical switches that provide a solution for a M×N switch in which any of M inputs can be connected to any of N outputs.
U.S. Pat. No. 5,337,378 to Saito et al., titled: “Optical Fiber Switch Including Partitions for Restricting Surplus Fibers”, the disclosure of which is incorporated herein by reference in its entirety, describes a switch formed of two rectangular arrays. A first array includes N first fibers in predetermined vertical positions adapted to slide horizontally. A second array includes N second fibers in predetermined horizontal positions configured to move vertically. In order to achieve a connection between a pair of fibers, the desired first fiber is moved to the horizontal position of the second fiber and the second fiber is moved to the vertical position of the first fiber. Each of the arrays has a fiber movement system, which moves the desired fiber into its place.
The above discussed rectangular switches are relatively large and generally require special arrangements for storing excess fiber lengths.
U.S. Pat. No. 6,859,575 to Arol et al., titled: “Self Aligning Opto-Mechanical Crossbar Switch”, the disclosure of which is incorporated herein by reference in its entirety, describes an optical fiber switch having separate fiber movement units for each fiber. In one embodiment, this patent describes a cylindrical structure. A first set of fibers are arranged to slide around respective annular rings and a second set of fibers are arranged to slide linearly along bars on the periphery of a cylinder. Each fiber is associated with a motor which is used to move the fiber into place so that it is aligned with a corresponding fiber, thus providing a light path between a selected fiber from the first set and a selected fiber from the second set.
The cost of this switch is relatively high, as many controllers and motors are required. In addition, maintenance and trouble shooting are costly due to the large number of motors.